The present invention relates to an extended life swivel seal assembly and, in particular, to an extended life swivel seal assembly for use in a fluid coupling device for high speed geological drilling operations.
Fluid coupling devices are utilized in high speed drilling operations where it is necessary to couple the outlet of a fluid source to the rotating device. Specifically, in oil and gas drilling operations, swivel seal assemblies are utilized to provide a sealing arrangement between the washpipe and the rotating sealing housing.
One type of a drilling rig swivel seal assembly utilizes a stack of rotary seals which are typically comprised of reinforced elastomeric material that provide a dynamic sealing arrangement with the external cylindrical sealing surface of the washpipe. In such designs, the seals and their housings rotate relative to the stationary washpipe, and the seals are sequentially exposed to the high pressure drilling fluid on one side of the seal and atmospheric pressure on the other side of the seal. This differential pressure causes the seal closest to the high pressure to grab tightly against the washpipe, thereby causing a high degree of wear and abrasion to the washpipe and the seal. The relatively large clearance required between the rotating seal and the washpipe result in ultimate failure of the seal. Additionally, because of the stacked relation of the seals to the washpipe, once the first seal fails, the next seal in the stack is exposed to similar forces and wear and so on until all the seals have been consumed by the severe abrasive operating conditions. Also, such rotary seal members are complicated and complex in structure, are time consuming and difficult to replace, and have a limited lifetime of approximately 200 hours or less when operating at 90 RPM's and up to 2,500 PSI. When such seal assemblies are operated at 5,000 PSI and at 250 RPM's, such seals last only between 20 and 30 hours before replacement is necessary.
An additional sealing arrangement is the utilization of complex U-shaped cup ring sealing assemblies between the washpipe and the rotating seal assembly. However, such sealing assemblies also have a limited lifetime and require significant replacement costs due to wear and abrasion which results in extended downtime of the drilling swivel seal assembly.
It has also been suggested to provide a floating seal member attached to the rotating coupling member and a similar seal member mounted to the non-rotating coupling member to provide a seal assembly for a drilling rig swivel assembly. Such seal assemblies further include a secondary seal member comprised of a U-cup seal member between the distal end of the washpipe member and the floating seal member. However, because the U-cup seal member is exposed to the high pressure abrasive drilling fluid, such contact results in the rapid failure of such fluid coupling assemblies.